fixed converters

In #769, the converters applied to a controller are only applied if the name is part of the route placeholders. It was done to avoid executing converters on all controllers when applied to a controller collection.

That breaks BC (see #806) as the usual use case is now broken.

Instead of reverting #769, I propose to only execute converters when the converter name is an argument of the controller itself. That solves both problem: you can have global converters that are only applied when there is a matching argument in the controller, and you are not forced to use an existing route placeholder name for the controller argument name.